Process for the preparation of a 2-ethylaminopyridine derivative

ABSTRACT

Process for the preparation of a 2-ethylaminopyridine derivative of general formula (I) or a salt thereof 
                         
Process for the preparation of a N-[2-(2-pyridinyl)ethyl]carboxamide derivative of general formula (II) or a salt thereof
 
                         
Intermediate of general formula (III)

CROSS REFERENCE TO RELATED APPLICATION(S)

The present application is a 35 U.S.C. § 371 national phase conversion of PCT/EP2005/056900 filed Dec. 19, 2005, which claims priority of European Application No. 04356202.4 filed Dec. 21, 2004.

The present invention relates to a novel process for the preparation of 2-ethylaminopyridine derivative which is useful as an intermediate compound for the preparation of pesticides, starting with 2-halogenopyridine derivative.

Patent application WO 2004/016088 discloses the preparation of N-[2-(2-pyridinyl)ethyl]benzamide derivatives starting from 2-halogenopyridine derivatives to produce 2-ethylaminopyridine derivatives and then coupling these 2-ethylaminopyridine derivatives with a halogenobenzoyl derivative. A step of this process consists in the reduction of a 2-methylcyanopyridine derivative into a 2-ethylaminopyridine in the presence of a metal catalyst in a protic solvent.

The process disclosed in this patent application presents the drawback in that the yield of the step of reduction of the 2-methylcyanopyridine derivative to produce a 2-ethylaminopyridine derivative is low and not acceptable at an industrial scale.

The process disclosed in this patent application also presents the drawback in that two separate steps are necessary for the preparation of the 2-methylcyanopyridine derivative starting from the 2-halogenopyridine derivative. This consequently increase the costs of the process and decrease its global yield, which is not acceptable at an industrial scale.

We have now found an alternative method to prepare 2-ethylaminopyridine derivative which overcomes these problems and which is applicable to industrial scale operation.

Accordingly, the present invention relates to a process for the preparation of a 2-ethylaminopyridine derivative of general formula (I) or a salt thereof

in which:

-   -   p is an integer equal to 1, 2, 3 or 4;     -   X is the same or different and is a hydrogen atom, a halogen         atom, a nitro group, a cyano group, a hydroxy group, an amino         group, a sulfanyl group, a pentafluoro-λ⁶-sulfanyl group, a         formyl group, a formyloxy group, a formylamino group, a carboxy         group, a carbamoyl group, a N-hydroxycarbamoyl group, a         carbamate group, a (hydroxyimino)-C₁-C₆-alkyl group, a         C₁-C₈-alkyl, a C₁-C₈-halogenoalkyl having 1 to 5 halogen atoms,         a C₂-C₈-alkenyl, a C₂-C₈-alkynyl, a C₁-C₈-alkylamino, a         di-C₁-C₈-alkylamino, a C₁-C₈-alkoxy, a C₁-C₈-halogenoalkoxy         having 1 to 5 halogen atoms, a C₁-C₈-alkylsulfanyl, a         C₁-C₈-halogenoalkylsulfanyl having 1 to 5 halogen atoms, a         C₂-C₈-alkenyloxy, a C₂-C₈-halogenoalkenyloxy having 1 to 5         halogen atoms, a C₃-C₈-alkynyloxy, a C₃-C₈-halogenoalkynyloxy         having 1 to 5 halogen atoms, a C₃-C₈-cycloalkyl, a         C₃-C₈-halogenocycloalkyl having 1 to 5 halogen atoms, a         C₁-C₈-alkylcarbonyl, a C₁-C₈-halogenoalkylcarbonyl having 1 to 5         halogen atoms, a C₁-C₈-alkylcarbamoyl, a         di-C₁-C₈-alkylcarbamoyl, a (N—C₁-C₈-alkyl)oxycarbamoyl, a         C₁-C₈-alkoxycarbamoyl, a (N—C₁-C₈-alkyl)-C₁-C₈-alkoxycarbamoyl,         a C₁-C₈-alkoxycarbonyl, a C₁-C₈-halogenoalkoxycarbonyl having 1         to 5 halogen atoms, a C₁-C₈-alkylcarbonyloxy, a         C₁-C₈-halogenoalkylcarbonyloxy having 1 to 5 halogen atoms, a         C₁-C₈-alkylcarbonylamino, a C₁-C₈-halogenoalkylcarbonylamino         having 1 to 5 halogen atoms, a C₁-C₈-alkylaminocarbonyloxy, a         di-C₁-C₈-alkylaminocarbonyloxy, a C₁-C₈-alkyloxycarbonyloxy, a         C₁-C₈-alkylsulphenyl, a C₁-C₈-halogenoalkylsulphenyl having 1 to         5 halogen atoms, a C₁-C₈-alkylsulphinyl, a         C₁-C₈-halogenoalkylsulphinyl having 1 to 5 halogen atoms, a         C₁-C₈-alkylsulphonyl, a C₁-C₈-halogenoalkyl-sulphonyl having 1         to 5 halogen atoms, a (C₁-C₆-alkoxyimino)-C₁-C₆-alkyl, a         (C₁-C₆-alkenyloxyimino)-C₁-C₆-alkyl, a         (C₁-C₆-alkynyloxyimino)-C₁-C₆-alkyl, a         (benzyloxyimino)-C₁-C₆-alkyl, a benzyloxy, a benzylsulfanyl, a         benzylamino, a phenoxy, a phenylsulfanyl or a phenylamino; and

as to the N-oxides of 2-pyridine thereof; said process comprising:

(A)—a first step according to reaction scheme 1:

in which:

-   -   X and p are as defined above;     -   R is a C₁-C₈-alkyl; and     -   Hal represents a halogen atom;         comprising:

a) the reaction of a 2-halogenopyridine derivative with an alkyl cyanoacetate, in a 2-halogenopyridine derivative/alkyl cyanoacetate molar ratio of from 1 to 10, in a polar solvent, in the presence of a base, the base/2-halogenopyridine derivative molar ratio being of from 1 to 4;

b) followed by an addition of acid until a pH value of the reaction mixture of from 1 to 5;

to provide a 2-methylcyanopyridine derivative;

(B)—a second step according to reaction scheme 2:

in which:

-   -   X, p are as defined above;     -   R¹ represents a C₁-C₆-alkyl;     -   R² represents a halogen atom or a —OCOAlk group; and     -   Alk represents a C₁-C₆-alkyl;         comprising the catalytic reduction of reaction of a         2-methylcyanopyridine derivative obtained in step one in the         presence of an acylating agent of formula R¹COR² and of a         catalyst, in a solvent, under a hydrogen pressure of from 4 to         40 bar, to provide a 2-ethylaminopyridyl derivative;         (C)—a third step according to reaction scheme 3:

in which:

-   -   X and p are as defined above; and     -   R¹ represents a C₁-C₆-alkyl;         comprising the hydrolysis in water of a 2-ethylaminopyridine         derivative obtained in step two by adding to it from 1 to 20         molar equivalent of an acid, at a temperature of from 20° C. to         reflux, to provide a compound of general formula (I).

For the purposes of the present invention:

-   -   a halogen atom may be a bromine atom, a chlorine atom, a iodine         atom or a fluorine atom. Preferably, halogen atom means chlorine         atom;     -   carboxy means —C(═O)OH;     -   carbonyl means —C(═O)—;     -   carbamoyl means —C(═O)NH₂;     -   N-hydroxycarbamoyl means —C(═O)NHOH; and     -   an alkyl group, an alkenyl group, and an alkynyl group as well         as moieties containing these terms, can be linear or branched.

During the preparation of compound of general formula (I) according to the present invention, the preparation of the 2-methylcyanopyridine derivative starting from the 2-halogenopyridine derivative is made in only one step. Furthermore, the yield of the reduction step of a 2-methylcyanopyridine derivative into a 2-ethylaminopyridine derivative is of 65% to 95%. Such a process can thus be used at an industrial scale.

According to the present invention, the 2-pyridyl moiety may be substituted in any position by (X)_(p), in which X and n are as defined above. Preferably, the present invention relates to the preparation of 2-ethylaminopyridine derivative of general formula (I) in which the different characteristics may be chosen alone or in combination as being:

-   -   as regards p, p is 1, 2 or 3. Preferably, p is 2.     -   as regards X, X is chosen, independently of the others, as being         a halogen atom, a C₁-C₈-alkyl or a C₁-C₈-halogenoalkyl having 1         to 5 halogen atoms. More preferably, X is chosen, independently         of the others, as being chlorine or CF₃;     -   as regards the positions in which the 2-pyridyl moiety is         substituted by X, the 2-pyridyl moiety is substituted by X in 3-         and/or in 5-position. Preferably, the 2-pyridyl moiety is         substituted by X in 3- and 5-position

The process of the present invention is particularly suitable for the preparation of:

-   -   N-2-[3-chloro-5-(trifluoromethyl)-2-pyridinyl]ethylamine, or     -   N-2-[3,5-dichloro-2-pyridinyl]ethylamine.

The first step (step A) of the process according to the present invention comprises the reaction of a 2-halogenopyridine derivative with an alkyl cyanoacetate, in a 2-halogenopyridine derivative/alkyl cyanoacetate molar ratio of from 1 to 10, in a polar solvent, in the presence of a base, the base/2-halogenopyridine derivative molar ratio being of from 1 to 4; followed by an addition of acid until a pH value of the reaction mixture of from 1 to 5 to provide a 2-methylcyanopyridine derivative. Preferably, step A may be conducted in the following conditions, chosen alone or in combination:

-   -   the polar solvent is chosen as being dimethylsulfoxide (DMSO),         an ether solvent, an amide solvent or an urea solvent. More         preferably, the solvent is chosen as being dimethylsulfoxide         (DMSO), diethyl ether, diisopropyl ether, methyl         tert-butyl-ether, methyl tert-amyl-ether, dioxane,         tetrahydrofuran (THF), 1,2-di-methoxyethane,         1,2-di-ethoxy-ethane, anisole, N,N-dimethyl-formamide,         N,N-dimethyl-acetamide, N-methyl-formanilide,         N-methyl-pyrrolidone (NMP), hexamethyl-phosphoric-triamide or         1,3-dimethyl-2-2imidazolinone (DMA). Even more preferably, the         solvent is chosen as being tetrahydrofuran (THIF),         N-methyl-pyrrolidone (NMP), 1,3-dimethyl-2-2imidazolinone (DMA)         or dimethylsulfoxide (DMSO);     -   the 2-halogenopyridine derivative/alkyl cyanoacetate molar ratio         of from 1 to 5;     -   the alkyl cyanoacetate is chosen as being methylcyanoacetate,         ethylcyanoacetate or terbutylcyanoacetate;     -   the base is chosen as being a alkaline earth metal base, a         alkali metal hydride base, a hydroxide base, an amide base, an         alcoholate base, an acetate base, a carbonate base, a hydrogen         carbonate base or a tertiary amine base. More preferably, the         base is chosen as being hydrogen carbonate base includes sodium         hydride, sodium amide, lithium diisoproylamide, sodium         methanolate, sodium ethanolate, potassium tert-butanolate,         sodium acetate, potassium acetate, calcium acetate, sodium         hydroxide, potassium hydroxide, sodium carbonate, potassium         carbonate, potassium bicarbonate, sodium bicarbonate, ammonium         carbonate, trimethylamine, triethylamine, tributyl-amine,         N,N-dimethyl-aniline, N,N-di-methyl-benzylamine pyridine,         N-methylpiperidine, N-methyl-morpholine,         N,N-dimethylaminopyridine, diazabicyclooctane (DABCO),         diazabicyclononene (DBN) or diazabicycloundecene (DBU). Even         more preferably, the base is chosen as being potassium         hydroxide, sodium hydroxide, potassium bicarbonate, sodium         bicarbonate or sodium hydride;     -   the base/2-halogenopyridine derivative molar ratio is of from 1         to 2.5;     -   the acid added is a mineral acid. Suitable mineral acid includes         HCl and H₂SO₄. More preferably, HCl is added;     -   the acid is added until a pH value of the reaction mixture of         from 2 to 4, more preferably of 2.

Step A does not necessarily require specific temperature conditions. Preferably, step A is conducted at a temperature of from 0° C. to reflux. More preferably, step A is conducted at a temperature of from 0° C. to 100° C.

The second step (step B) of the process according to the present invention comprises the catalytic reduction of reaction of a 2-methylcyanopyridine derivative obtained in step one in the presence of an acylating agent of formula R¹COR² and of a catalyst, in a solvent, under a hydrogen pressure of from 4 to 40 bar, to provide a 2-ethylaminopyridyl derivative. Preferably, step B may be conducted in the following conditions, chosen alone or in combination:

-   -   the catalyst is a metallic catalyst Suitable metallic catalyst         includes nickel-, platinum- or palladium-based catalyst such as         Raney nickel, rhodium on alumina, palladium on charcoal,         palladium on calcium carbonate, palladium on silica, palladium         hydroxide, platinum on charcoal or platinum on alumina. More         preferably, palladium on charcoal is used;     -   the solvent is an organic acid. More preferably, the solvent is         a C₁-C₆-alkanoic acid or formic acid. Suitable C₁-C₆-alkanoic         acid includes acetic acid, propanoic acid, butanoic acid,         pentanoic acid or hexanoic acid. Even more preferably, the         solvent is acetic acid;     -   the acylating agent is a C₁-C₆-alkanoic acid anhydride or formic         anhydride. Suitable C₁-C₆-alkanoic acid anhydride includes         acetic anhydride, propanoic anhydride, butanoic anhydride,         pentanoic anhydride or hexanoic anhydride. Even more preferably,         the acylating agent is acetic anhydride;     -   the hydrogen pressure is of from 4 to 35 bars.

Step B does not necessarily require specific temperature conditions. Preferably, step B is conducted at a temperature of from 16° C. to 70° C. More preferably, step B is conducted at a temperature of from 20° C. to 40° C.

The third step (step C) of the process according to the present invention comprises the hydrolysis in water of a 2-ethylaminopyridine derivative obtained in step two by adding to it from 1 to 20 molar equivalent of an acid, at a temperature of from 20° C. to reflux, to provide a compound of general formula (I). Preferably, step C may be conducted in the following conditions, chosen alone or in combination:

-   -   the added acid is a mineral acid. Suitable mineral acid includes         HCl, H₃PO₄, H₂SO₄, HBr, HI or HF. More preferably, the acid is         HCl or H₂SO₄. Even more preferably, the acid is HCl;     -   2 to 10 molar equivalents of acid are added the         2-ethylaminopyridinederivative obtained in step two (step B).         More preferably, 5 molar equivalents of acid are added the         2-ethylaminopyridine derivative obtained in step two (step B);     -   the reaction is conducted at reflux.

Compound of general formula (I) as defined above is a useful intermediate for the preparation of known pesticide compounds. These known pesticide compounds can be prepared by coupling a compound of general formula (I) as defined above with a halide benzoyl derivative. Thus, the present invention also relates to a process as defined above comprising a further step (D) according to the reaction scheme 4:

in which:

-   -   X and p are as defined above;     -   A represents a phenyl group or a 5-, 6- or 7-membered non-fused         heterocycle with one, two or three heteroatoms which may be the         same or different, the heterocycle being linked by a carbon         atom; each of this group being optionally substituted by one or         more substituents chosen independently of each other as being a         halogen atom, a nitro group, a cyano group, a hydroxy group, an         amino group, a sulfanyl group, a pentafluoro-λ⁶-sulfanyl group,         a formyl group, a formyloxy group, a formylamino group, a         carboxy group, a C₁-C₈-alkyl, a C₁-C₈-halogenoalkyl having 1 to         5 halogen atoms, a C₂-C₈-alkenyl, a C₂-C₈-alkynyl, a         C₁-C₈-alkylamino, a di-C₁-C₈-alkylamino, a C₁-C₈-alkoxy, a         C₁-C₈-halogenoalkoxy having 1 to 5 halogen atoms, a         C₁-C₈-alkoxy-C₂-C₈-alkenyl, a C₁-C₈-alkylsulfanyl, a         C₁-C₈-halogenoalkylsulfanyl having 1 to 5 halogen atoms, a         C₁-C₈-alkoxycarbonyl, a C₁-C₈-halogenoalkoxycarbonyl having 1 to         5 halogen atoms, a C₁-C₈-alkylcarbonyloxy, a         C₁-C₈-halogenoalkylcarbonyloxy having 1 to 5 halogen atoms, a         C₁-C₈-alkylsulphenyl, a C₁-C₈-halogenoalkylsulphenyl having 1 to         5 halogen atoms, a C₁-C₈-alkylsulphinyl, a         C₁-C₈-halogenoalkylsulphinyl having 1 to 5 halogen atoms, a         C₁-C₈-alkylsulphonyl, a C₁-C₈-halogenoalkylsulphonyl having 1 to         5 halogen atoms or a C₁-C₈-alkylsulfonamide;         comprising the coupling reaction of the 2-ethylaminopyridine         obtained in step three of the above described process with a         halide carboxyl derivative contained in an organic solvent in         the presence of a base to produce a         N-[2-(2-pyridinyl)ethyl]carboxamide derivative of general         formula (II).

According to the present invention, A may represent a five membered ring non-fused heterocycle. Specific examples of compounds prepared according to the process of the present invention where A is a five membered heterocycle include compound of general formula (II) wherein:

* A represents a heterocycle of the general formula (A-1)

in which:

-   -   R³ and R⁴ may be the same or different and may be a hydrogen         atom, a halogen atom, an amino group, a nitro group, a         C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5 halogen         atoms; and     -   R⁵ may be a halogen atom, a nitro group, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-2)

in which:

-   -   R⁶ may be a hydrogen atom, a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms; and     -   R⁷ and R⁸ may be the same or different and may be a hydrogen         atom, a halogen atom, an amino group, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-3)

in which:

-   -   R⁹ may be a halogen atom, a C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl         having 1 to 5 halogen atoms; and     -   R¹⁰ may be a hydrogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A4)

in which:

-   -   R¹¹ and R¹² may be the same or different and may be a hydrogen         atom, a halogen atom, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl         having 1 to 5 halogen atoms, a C₁-C₄-alkylthio, a         C₁-C₄-alkylsulphonyl, a phenyl optionally substituted by a         halogen atom or a C₁-C₄-alkyl or a pyridyl optionally         substituted by a halogen atom or a C₁-C₄-alkyl; and     -   R¹³ may be a halogen atom, a cyano group, a C₁-C₄-alkyl, a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms or a         C₁-C₄-halogenoalkoxy having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-5)

in which:

-   -   R¹⁴ and R⁵ may be the same or different and may be a hydrogen         atom, a halogen atom, a C₁-C₄-alkyl, a C₁-C₄-alkyloxy or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms; and     -   R¹⁶ may be a hydrogen atom, a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-6)

in which:

-   -   R¹⁷ may be a hydrogen atom, a halogen atom, a cyano group, a         C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5 halogen         atoms;     -   R¹⁸ and R²⁰ may be the same or different and may be a hydrogen         atom, a halogen atom, a C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl         having 1 to 5 halogen atoms; and     -   R¹⁹ may be a hydrogen atom, a cyano group, a C₁-C₄-alkyl, a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms, a         C₁-C₄-alkoxy-C₁-C₄-alkyl, a hydroxy-C₁-C₄-alkyl, a         C₁-C₄-alkylsulphonyl, a di(C₁-C₄-alkyl)aminosulphonyl, a         C₁-C₆-alkylcarbonyl, a phenylsulphonyl optionally substituted by         a halogen atom or a C₁-C₄-alkyl, or a benzoyl optionally         substituted by a halogen atom or a C₁-C₄-alkyl.         * A represents a heterocycle of the general formula (A-7)

in which:

-   -   R²¹ may be a hydrogen atom, a cyano group, a C₁-C₄-alkyl, a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms, a         C₁-C₄-alkoxy-C₁-C₄-alkyl, a hydroxy-C₁-C₄-alkyl, a         C₁-C₄-alkylsulphonyl, a di(C₁-C₄-alkyl)aminosulphonyl, a         C₁-C₆-alkylcarbonyl, a phenylsulphonyl optionally substituted by         a halogen atom or a C₁-C₄-alkyl, or a benzoyl optionally         substituted by a halogen atom or a C₁-C₄-alkyl; and     -   R²², R²³ and R²⁴ may be the same or different and may be a         hydrogen atom, a halogen atom, a cyano group, a C₁-C₄-alkyl, a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms or a         C₁-C₄-alkylcarbonyl.         * A represents a heterocycle of the general formula (A-8)

in which:

-   -   R²⁵ may be a hydrogen atom or a C₁-C₄-alkyl; and     -   R²⁶ may be a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-9)

in which:

-   -   R²⁷ may be a hydrogen atom or a C₁-C₄-alkyl; and     -   R²⁸ may be a halogen atom, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl         having 1 to 5 halogen atoms or a phenyl optionally substituted         by a halogen atom or a C₁-C₄-alkyl.         * A represents a heterocycle of the general formula (A-10)

in which:

-   -   R²⁹ may be a hydrogen atom, a halogen atom, an amino group, a         cyano group, a C₁-C₄-alkylamino, a di-(C₁-C₄-alkyl)amino, a         C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms         or a phenyl optionally substituted by a halogen atom or a         C₁-C₄-alkyl; and     -   R³⁰ may be a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-11)

in which:

-   -   R³¹ may be a hydrogen atom, a halogen atom, an amino group, a         cyano group, a C₁-C₄-alkylamino, a di-(C₁-C₄-alkyl)amino, a         C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5 halogen         atoms; and     -   R³² may be a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-12)

in which:

-   -   R³³ may be a halogen atom, a cyano group, a nitro group, a         C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms,         a C₃-C₆-cycloalkyl, a C₁-C₄-alkoxy, a C₁-C₄-halogenoalkoxy         having 1 to 5 halogen atoms, a C₁-C₄-alkylthio, a         C₁-C₄-halogenoalkylthio having 1 to 5 halogen atoms, an         aminocarbonyl group or an aminocarbonyl-C₁-C₄-alkyl;     -   R³⁴ may be a hydrogen atom, a halogen atom, a cyano group, a         nitro group, a C₁-C₄-alkyl, a C₁-C₄-alkoxy or a C₁-C₄-alkylthio;         and     -   R³⁵ may be a hydrogen atom, a phenyl, a C₁-C₄-alkyl, a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms, a         hydroxy-C₁-C₄-alkyl, a C₂-C₆-alkenyl, a C₃-C₆-cycloalkyl, a         C₁-C₄-alkylthio-C₁-C₄-alkyl, a         C₁-C₄-halogenoalkylthio-C₁-C₄-alkyl having 1 to 5 halogen atoms,         a C₁-C₄-alkoxy-C₁-C₄-alkyl or a C₁-C₄-halogenoalkoxy-C₁-C₄-alkyl         having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-13)

in which:

-   -   R³⁶ may be a hydrogen atom, a halogen atom, a cyano group, a         nitro group, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5         halogen atoms, a C₃-C₆-cycloalkyl, a C₁-C₄-alkoxy, a         C₁-C₄-halogenoalkoxy having 1 to 5 halogen atoms, a         C₁-C₄-alkylthio, a C₁-C₄-halogenoalkylthio having 1 to 5 halogen         atoms, an aminocarbonyl or an aminocarbonyl-C₁-C₄-alkyl;     -   R³⁷ may be a hydrogen atom, a halogen atom, a cyano group, a         C₁-C₄-alkyl, a C₁-C₄-alkoxy, a C₁-C₄-halogenoalkoxy having 1 to         5 halogen atoms or a C₁-C₄-alkylthio; and     -   R³⁸ may be a hydrogen atom, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl         having 1 to 5 halogen atoms, a hydroxy-C₁-C₄-alkyl, a         C₂-C₆-alkenyl, a C₃-C₆-cycloalkyl, a         C₁-C₄-alkylthio-C₁-C₄-alkyl, a         C₁-C₄-halogenoalkylthio-C₁-C₄-alkyl having 1 to 5 halogen atoms,         a C₁-C₄-alkoxy-C₁-C₄-alkyl, a C₁-C₄-halogenoalkoxy-C₁-C₄-alkyl         having 1 to 5 halogen atoms or a phenyl optionally substituted         by a halogen atom, a C₁-C₄-alkyl, a C₁-C₄-alkoxyalkyl or a nitro         group.         * A represents a heterocycle of the general formula (A-14)

in which:

-   -   R³⁹ may be a hydrogen atom, a halogen atom, a cyano group, a         nitro group, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5         halogen atoms, a C₃-C₆-cycloalkyl, a C₁-C₄-alkoxy, a         C₁-C₄-halogenoalkoxy having 1 to 5 halogen atoms, a         C₁-C₄-alkylthio, a C₁-C₄-halogenoalkylthio having 1 to 5 halogen         atoms, an aminocarbonyl, or an aminocarbonyl-C₁-C₄-alkyl;     -   R⁴⁰ may be a hydrogen atom, a halogen atom, a cyano group, a         C₁-C₄-alkyl, a C₁-C₄-alkoxy, a C₁-C₄-alkylthio or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms;     -   R⁴¹ may be a hydrogen atom, a phenyl, a benzyl, a C₁-C₄-alkyl, a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms, a         hydroxy-C₁-C₄-alkyl, a C₂-C₆-alkenyl, a C₃-C₆-cycloalkyl, a         C₁-C₄-alkylthio-C₁-C₄-alkyl, a         C₁-C₄-halogenoalkylthio-C₁-C₄-alkyl having 1 to 5 halogen atoms,         a C₁-C₄-alkoxy-C₁-C₄-alkyl, a C₁-C₄-halogenoalkoxy-C₁-C₄-alkyl         having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-15)

in which:

-   -   R⁴² may be a hydrogen atom, a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms; and

R⁴³ may be a halogen atom, a C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.

* A represents a heterocycle of the general formula (A-16)

in which R⁴⁴ and R⁴⁵ may be the same or different and may be a hydrogen atom, a halogen atom, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms, a phenyl optionally substituted by a halogen atom or a C₁-C₄-alkyl, or a heterocyclyl optionally substituted by a halogen atom or a C₁-C₄-alkyl.

* A represents a heterocycle of the general formula (A-17)

in which

-   -   R⁴⁶ may be a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms. and     -   R⁴⁷ may be a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.         * A represents a heterocycle of the general formula (A-18)

in which R⁴⁸ may be a halogen atom, a C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.

* A represents a heterocycle of the general formula (A-19)

in which:

-   -   R⁴⁹ may be a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms; and     -   R⁵⁰ may be a hydrogen atom, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl         having 1 to 5 halogen atoms, or a phenyl optionally substituted         by a halogen atom or a C₁-C₄-alkyl.         * A represents a heterocycle of the general formula (A-20)

in which R⁵¹ may be a halogen atom, a C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.

According to the present invention, A may also represent a six membered ring non-fused heterocycle. Specific examples of compounds prepared according to the process of the present invention where A is a six membered heterocycle include:

* A represents a heterocycle of the general formula (A-21)

in which:

-   -   R⁵² may be a halogen atom, a hydroxy group, a cyano group, a         C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms,         a C₁-C₄-alkoxy, a C₁-C₄-alkylthio, a C₁-C₄-halogenoalkylthio         having 1 to 5 halogen atoms or a C₁-C₄-halogenoalkoxy having 1         to 5 halogen atoms;     -   R⁵³, R⁵ and R⁵⁵, which may be the same or different, may be a         hydrogen atom, a halogen atom, a cyano group, a C₁-C₄-alkyl, a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms, a C₁-C₄-alkoxy,         a C₁-C₄-alkylthio, a C₁-C₄-halogenoalkoxy having 1 to 5 halogen         atoms, a C₁-C₄-alkylsulphinyl or a C₁-C₄-alkylsulphonyl.         * A represents a heterocycle of the general formula (A-22)

in which:

-   -   R⁵⁶ may be a hydrogen atom, a halogen atom, a hydroxy group, a         cyano group, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5         halogen atoms, a C₁-C₄-alkoxy, a C₁-C₅-alkylthio, a         C₂-C₅-alkenylthio a C₁-C₄-halogenoalkylthio having 1 to 5         halogen atoms, a C₁-C₄-halogenoalkoxy having 1 to 5 halogen         atoms, a phenyloxy optionally substituted by a halogen atom or a         C₁-C₄-alkyl, or a phenylthio optionally substituted by a halogen         atom or a C₁-C₄-alkyl;     -   R⁵⁷, R⁵⁸ and R⁵⁹, which may the same or different, may be a         hydrogen atom, a halogen atom, a cyano group, a C₁-C₄-alkyl, a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms, a C₁-C₄-alkoxy,         a C₁-C₄-alkylthio, a C₁-C₄-halogenoalkoxy having 1 to 5 halogen         atoms, a C₁-C₄-alkylsulphinyl, a C₁-C₄-alkylsulphonyl or a         N-morpholine optionally substituted by a halogen atom or a         C₁-C₄-alkyl, or a thienyl optionally substituted by a halogen         atom or a C₁-C₄-alkyl.         * A represents a heterocycle of the general formula (A-23)

in which R⁶⁰, R⁶¹, R⁶² and R⁶³, which may be the same or different, may be a hydrogen atom, a halogen atom, a hydroxy group, a cyano group, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms, a C₁-C₄-alkoxy, a C₁-C₄-alkylthio, a C₁-C₄-halogenoalkylthio having 1 to 5 halogen atoms, a C₁-C₄-halogenoalkoxy having 1 to 5 halogen atoms, a C₁-C₄-alkylsulphinyl or a C₁-C₄-alkylsulphonyl.

* A represents a heterocycle of the general formula (A-24)

in which:

-   -   R⁶⁴ may be a halogen atom, a C₁-C₄-alkyl or a         C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms;     -   R⁶⁵ may be a hydrogen atom, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl         having 1 to 5 halogen atoms, a C₁-C₆-alkoxycarbonyl, a benzyl         optionally substituted by 1 to 3 halogen atoms, a         benzyloxycarbonyl optionally substituted by 1 to 3 halogen atoms         or a heterocyclyl.         * A represents a heterocycle of the general formula (A-25)

in which:

-   -   R⁶⁶ may be a halogen atom, a hydroxy group, a cyano group, a         C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms,         a C₁-C₄-alkoxy, a C₁-C₄-alkylthio, a C₁-C₄-halogenoalkylthio         having 1 to 5 halogen atoms or a C₁-C₄-halogenoalkoxy having 1         to 5 halogen atoms;

R⁶⁷ may be a hydrogen atom, a C₁-C₄-alkyl, a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms or a benzyl.

* A represents a heterocycle of the general formula (A-26)

in which:

-   -   X¹ may be a sulphur atom, —SO—, —SO₂— or —CH₂—;     -   R⁶⁸ may be a C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5         halogen atoms; and     -   R⁶⁹ and R⁷⁰ may be the same or different and may be a hydrogen         atom or a C₁-C₄-alkyl.         * A represents a heterocycle of the general formula (A-27)

in which:

-   -   R⁷¹ may be a C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5         halogen atoms;         * A represents a heterocycle of the general formula (A-28)

in which:

-   -   R⁷² may be a C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5         halogen atoms.         * A represents a heterocycle of the general formula (A-29)

in which R⁷³ may be a halogen atom, a C₁-C₄-alkyl or a C₁-C₄-halogenoalkyl having 1 to 5 halogen atoms.

According to the present invention, A may also represent an optionally substituted phenyl group. Preferably, the present invention relates to the preparation of N-[2-(2-pyridinyl)ethyl]carboxamide derivative of general formula (II) in which A is a phenyl group and in which the different characteristics may be chosen alone or in combination as being:

A is substituted by 1 or 2 substituents. More preferably, A is substituted by 1 substituent.

each substituent is chosen, independently of the others, as being a hydrogen atom, a halogen atom, a C₁-C₈-alkyl or a C₁-C₈-halogenoalkyl having 1 to 5 halogen atoms. More preferably each substituent is chosen, independently of the others, as being chlorine or CF₃;

the phenyl moiety is substituted in ortho position.

Such a process is particularly suitable for the preparation of a compound of formula (II) which is:

-   -   N-{2-[3-chloro-5-(trifluoromethyl)-2-pyridinyl]ethyl}-2-trifluoromethylbenzamide;     -   N-{2-[3-chloro-5-(trifluoromethyl)-2-pyridinyl]ethyl}-2-iodobenzamide;         or     -   N-{2-[3,5-dichloro-2-pyridinyl]ethyl}-2-trifluoromethylbenzamide.

The fourth step (step D) of the process according to the present invention comprises the coupling reaction the 2-ethylaminopyridine obtained in step C with a halide benzoyl derivative to provide a compound of general formula (II) as defined above. Such a coupling reaction may be performed by known methods. Such a coupling reaction may for example be conducted according to the Schotten-Baumann reaction described in Schotten Ber. 1884, 17, 2544 and Baumann Ber. 1886, 19, 3218, herein incorporated by reference.

The compounds of general formula (I) and of formula (II) according to the present invention can be prepared according to the above described process. It will nevertheless be understood that, on the basis of his general knowledge and of available publications, the skilled worker will be able to adapt this method according to the specifics of each of the compounds, which it is desired to synthesise.

Certain of the intermediates used for the preparation of compound of general formula (I) are novel. Therefore, the present invention also relates to novel intermediate compounds useful for the preparation of compound of general formula (I). Thus, according to the present invention, there is provided a compound of general formula (III)

in which:

-   -   X and p are as defined above; and     -   R¹ represents a C₁-C₆-alkyl group.

The present invention will now be illustrated with reference to the following examples.

Preparation, of 3-chloro-5-(trifluoromethyl)-2-ethylamine-pyridinyl Step 1: Preparation of a 3-chloro-5-(trifluoromethyl)-2-methylcyanopyridine

A two-necked round bottom flask equipped with a magnetic bar, a thermometer and a reflux condenser was charged with the 2,3-dichloro-5-(trifluoromethyl)-pyridine in NMP (14.6% w/v), KOH (2.2 equiv.). The solution was heated to 70° C. and the ethyl cyanoacetate (1.2 equiv.) was added slowly. After the addition the reaction medium was heated 3 h. HCl aq. 36% was added to obtained pH 2 and the mixture was heated to 130° C. for 2 h. At 20° C., NaOH aq. 1N was added and the aqueous phase was extracted 3 times with methyl tertbutyl ether (MTBE). The organic phases were combined, washed with water, dried over MgSO₄ and concentrated to the dryness. The isolated yield was 94%.

NMR¹H (300 Mz, CDCl₃): 4.15 (s, 2H, CH ₂), 8.0 (s, 1H, Hpyr.), 8.79 (s, 1H, Hpyr.).

Step 2: Preparation of a 3-chloro-5-(trifluoromethyl)-2-ethylacetamide-pyridinyl

A hydrogenation reactor was charged with 3-chloro-5-trifluoromethyl-2-methylcyano pyridine (7 g, 31.4 mMol), Pd/C₅% (1.05 g), Ac₂O (12.8 g, 125.8 mMol, 4 equiv.), AcOH (60 ml). The reactor was stirred under 30 bars of hydrogen at 20° C. for 5 hours. The hydrogen was removed, the catalyst filtrated out and the solvent was evaporated. 8.4 g of crude desired product was obtained. HPLC titrated yield=71%.

Mass spectrum: 266 DA, MH⁺: 267

Step 3: Preparation of a 3-chloro-5-(trifluoromethyl)-2-ethylamine-pyridinyl

A two-necked round bottom flask equipped with a magnetic bar, a thermometer and a reflux condenser was charged with the above crude 3-chloro-5-(trifluoromethyl)-2-ethylacetamide-pyridinyl (22.2 mMol), water (50 ml), HCl 37% (4.3 g, 5 equiv.). The solution was refluxed 5 hours. The aqueous phase was washed 3 times with CH₂Cl₂ (3×20 ml) at room temperature. The aqueous phase was titrated by HPLC. The titrated yield in solution is 92%.

Mass spectrum analysis: 224 DA, MH⁺225.

Under these conditions, the global yield to prepare the 2-ethylaminopyridyl derivative starting from 2-methylcyanopyridine derivative (step 2 and step 3) is 65%, which is acceptable at an industrial scale.

Comparative experiments by using the process disclosed in patent application WO 2004/016088 have been conducted:

Preparation of a 3-chloro-5-trifluoromethyl)-2-ethylamine-pyridinyl starting from 3-chloro-5-(trifluoromethyl)-2-methylcyanopyridine according to the process disclosed in WO 2004/016088

A hydrogenation reactor was charged with 3-chloro-5-trifluoromethyl-2-methylcyano pyridine (1.5 g, 6.72 mMol), Pd/C₅%, AcOH (7 ml). The reactor was stirred under 6 bars of hydrogen at 20° C. for 15 hours. The hydrogen was removed, the catalyst filtrated out and the solvent was evaporated. 1.4 g of crude desired product was obtained. Titrated yield by HPLC is 19%.

Mass spectrum analysis: 224 DA, MH⁺225.

Under these conditions, the global yield to prepare the 2-ethylaminopyridyl derivative starting from 2-methylcyanopyridine derivative is only 19%, which is not acceptable at an industrial scale.

Above described step 3 may be completed by a further step for preparing N-{2-[3-chloro-5-(trifluoromethyl)-2-pyridinyl]ethyl}-2-trifluoromethylbenzamide which is known as fungicide:

Step 4: Preparation of a N-{2-[3-chloro-5-(trifluoromethyl)-2-pyridinyl]ethyl}-2-trifluoromethylbenzamide

A two-necked round bottom flask equipped with a magnetic bar, a thermometer and a reflux condenser was charged with the above aqueous solution, the 2-trifluoromethyl benzoic acid chloride (1.2 eq.) solution in THF (80 ml) was added followed by NaOH aqueous 2N until pH is 8. After 1 hour, the aqueous phase was extracted with iPr₂O (40 ml), the organic phases were mixed, washed with HCl aqueous 1N (2×40 ml) and water (40 ml). The organic phase was titrated by HPLC. The titrated yield in solution was 90%.

Heptane (70 ml) was added to the organic solution and the THF and iPr₂O were distilled to obtain precipitation of the desired compound. After filtration, the cake was washed with heptane/CH₂Cl₂ (90/10) and dried. The isolated yield was 80%. 

1. A process for the preparation of a 2-ethylaminopyridine derivative of general formula (I) or a salt thereof

in which: p is an integer equal to 1, 2, 3 or 4; X is independently selected from the group consisting of a hydrogen atom, a halogen atom, a nitro group, a cyano group, a hydroxy group, an amino group, a sulfanyl group, a pentafluoro-λ⁶-sulfanyl group, a formyl group, a formyloxy group, a formylamino group, a carboxy group, a carbamoyl group, a N-hydroxycarbamoyl group, a carbamate group, a (hydroxyimino)-C₁-C₆-alkyl group, a C₁-C₈-alkyl, a C₁-C₈-halogenoalkyl having 1 to 5 halogen atoms, a C₂-C₈-alkenyl, a C₂-C₈-alkynyl, a C₁-C₈-alkylamino, a di-C₁-C₈-alkylamino, a C₁-C₈-alkoxy, a C₁-C₈-halogenoalkoxy having 1 to 5 halogen atoms, a C₁-C₈-alkylsulfanyl, a C₁-C₈-halogenoalkylsulfanyl having 1 to 5 halogen atoms, a C₂-C₈-alkenyloxy, a C₂-C₈-halogenoalkenyloxy having 1 to 5 halogen atoms, a C₃-C₈-alkynyloxy, a C₃-C₈-halogenoalkynyloxy having 1 to 5 halogen atoms, a C₃-C₈-cycloalkyl, a C₃-C₈-halogenocycloalkyl having 1 to 5 halogen atoms, a C₁-C₈-alkylcarbonyl, a C₁-C₈-halogenoalkylcarbonyl having 1 to 5 halogen atoms, a C₁-C₈-alkylcarbamoyl, a di-C₁-C₈-alkylcarbamoyl, a (N—C₁-C₈-alkyl)oxycarbamoyl, a C₁-C₈-alkoxycarbamoyl, a (N—C₁-C₈-alkyl)-C₁-C₈-alkoxycarbamoyl, a C₁-C₈-alkoxycarbonyl, a C₁-C₈-halogenoalkoxycarbonyl having 1 to 5 halogen atoms, a C₁-C₈-alkylcarbonyloxy, a C₁-C₈-halogenoalkylcarbonyloxy having 1 to 5 halogen atoms, a C₁-C₈-alkylcarbonylamino, a C₁-C₈-halogenoalkylcarbonylamino having 1 to 5 halogen atoms, a C₁-C₈-alkylaminocarbonyloxy, a di-C₁-C₈-alkylaminocarbonyloxy, a C₁-C₈-alkyloxycarbonyloxy, a C₁-C₈-alkylsulphenyl, a C₁-C₈-halogenoalkylsulphenyl having 1 to 5 halogen atoms, a C₁-C₈-alkylsulphinyl, a C₁-C₈-halogenoalkylsulphinyl having 1 to 5 halogen atoms, a C₁-C₈-alkylsulphonyl, a C₁-C₈-halogenoalkylsulphonyl having 1 to 5 halogen atoms, a (C₁-C₆-alkoxyimino)-C₁-C₆-alkyl, a (C1-C6-alkenyloxyimino)-C₁-C₆-alkyl, a (C₁-C₆-alkynyloxyimino)-C₁-C₆-alkyl, a (benzyloxyimino)-C₁-C₆-alkyl, a benzyloxy, a benzylsulfanyl, a benzylamino, a phenoxy, a phenylsulfanyl and a phenylamino; and as to the N-oxides of 2-pyridine thereof; said process comprising: (A) a first step according to reaction scheme 1

in which: X and p are as defined above; R is a C₁-C₈-alkyl; and Hal represents a halogen atom; comprising: a) the reaction of a 2-halogenopyridine derivative with an alkyl cyanoacetate, in a 2-halogenopyridine derivative/alkyl cyanoacetate molar ratio of from 1 to 10, in a polar solvent, in the presence of a base, the base/2-halogenopyridine derivative molar ratio being of from 1 to 4; b) followed by an addition of acid until a pH value of the reaction mixture of from 1 to 5; to provide a 2-methylcyanopyridine derivative; wherein said first step (A) is conducted at a temperature of from 0° C. to reflux; (B) a second step according to reaction scheme 2:

in which: X and p are as defined above; R¹ represents a C₁-C₆-alkyl; R2 represents a halogen atom or a —OCOAlk group; and Alk represents a C₁-C₆-alkyl; comprising the catalytic reduction of reaction of a 2-methylcyanopyridine derivative obtained in the first step in the presence of an acylating agent of formula R¹COR² and of a catalyst, in a solvent, under a hydrogen pressure of from 4 to 40 bar, to provide a 2-ethylaminopyridyl derivative; (C) a third step according to reaction scheme 3:

in which: X and p are as defined above; and R¹ represents a C₁-C₆-alkyl group; comprising the hydrolysis in water of a 2-ethylaminopyridine derivative obtained in the second step by adding to it from 1 to 20 molar equivalent of an acid, at a temperature of from 20° C. to reflux, to provide a compound of general formula (I).
 2. The process claim 1 wherein p is
 2. 3. The process of claim 1 wherein each X is independently selected from the group consisting of chlorine and CF₃.
 4. The process claim 1 wherein the 2-pyridyl moiety is substituted by X in the 3-and/or in the 5-position.
 5. The process of claim 1 wherein the compound of formula (I) is selected from the group consisting of: N-2[3-chloro-5-(trifluoromethyl)-2-pyridinyl]ethylamine, and N-2-[3,5-dichloro-2-pyridinyl]ethylamine.
 6. The process of claim 1, wherein the second step (B) is conducted at a temperature of from 16° C. to 70° C.
 7. The process claim 1 further comprising a step (D) according to the reaction scheme 4:

in which: X and p are as defined above; A is selected from the group consisting of a phenyl group and a 5-, 6-or 7-membered non-fused heterocycle having one, two or three heteroatoms which may be the same or different, the heterocycle being linked by a carbon atom; each of this group being optionally substituted by one or more substituents independently selected from the group consisting of a halogen atom, a nitro group, a cyano group, a hydroxy group, an amino group, a sulfanyl group, a pentafluoro-λ⁶-sulfanyl group, a formyl group, a formyloxy group, a formylamino group, a carboxy group, a C₁-C₈-alkyl, a C₁-C₈-halogenoalkyl having 1 to 5 halogen atoms, a C₂-C₈-alkenyl, a C₂-C₈-alkynyl, a C₁-C₈-alkylamino, a di-C₁-C₈-alkylamino, a C₁-C₈-alkoxy, a C₁-C₈-halogenoalkoxy having 1 to 5 halogen atoms, a C₁-C₈-alkoxy-C₂-C₈-alkenyl, a C₁-C₈-alkylsulfanyl, a C₁-C₈-halogenoalkylsulfanyl having 1 to 5 halogen atoms, a C₁-C₈-alkoxycarbonyl, a C₁-C₈-halogenoalkoxycarbonyl having 1 to 5 halogen atoms, a C₁-C₈-alkylcarbonyloxy, a C₁-C₈-halogenoalkylcarbonyloxy having 1 to 5 halogen atoms, a C₁-C₈-alkylsulphenyl, a C₁-C₈-halogenoalkylsulphenyl having 1 to 5 halogen atoms, a C₁-C₈-alkylsulphinyl, a C₁-C₈-halogenoalkylsulphinyl having 1 to 5 halogen atoms, a C₁-C₈-alkylsulphonyl, a C₁-C₈-halogenoalkylsulphonyl having 1 to 5 halogen atoms and a C₁-C₈-alkylsulfonamide; comprising the coupling reaction of the 2-ethylaminopyridine obtained in the third step of said process of claim 1 with a halide carboxyl derivative contained in an organic solvent in the presence of a base to produce a N-[2-(2-pyridinylethyl]carboxamide derivative of general formula (II).
 8. The process claim 7 wherein A is a phenyl group.
 9. The process of claim 8 wherein A is substituted by one or two substituents.
 10. The process of claim 8 wherein each substituent of A is independently selected from the group consisting of chlorine and CF₃.
 11. The process of claim 8 wherein the A is substituted in an ortho position.
 12. The process of claim 7 wherein compound of formula (II) is selected from the group consisting of: N-{2[3-chloro-5-trifluoromethyl)-2-pyridinyl]ethyl}-2-trifluoromethylbenzamide; N-{2[3-chloro-5-trifluoromethyl)-2-pyridinyl]ethyl}-2-iodobenzamide; and N-{2-[3,5-dichloro-2-pyridinyl]ethyl}-2-trifluoromethylbenzamide. 